[ExI] Maximum biological lifespan

[Anders Sandberg]

On 2016-08-12 00:16, David Lubkin wrote:
> Do you see any inherent maximum active lifespan (that is, not in a 
> dormant state like a spore) for an evolved biological being?

Given how evolution works, multicellular organisms are likely but not 
guaranteed to age - once they have reproduced their importance to the 
eventual success to their genotype goes down drastically, so evolution 
does not prevent accumulation of mutations that mess them up later 
(=ageing). But as demonstrated by lobsters and some other organisms 
(sturgeon?) there is no reason why ageing might not occasionally fail to 
develop. Of course, the actual lifespan of non-ageing organisms is often 
more dominated by being killed by predators, accidents and disease: 
getting old enough to age significantly is a rare occurrence in nature.

So, no, there is no inherent maximum beyond the survival of the 
ecological niche the being lives in.

> How about for a conscious evolved biological being (that is, with 
> considerations of memory formation)?
A forgetful neural network can keep on learning forever.

> For instance, could there be a planet somewhere that naturally 
> developed a single, continual consciousness that has lasted a thousand 
> years? A million? A billion?
Perhaps. But it is not likely.

Remember that actual animal lifespans follow a fairly simple scaling law 
with body mass, L ~ M^0.15 to M^0.3. (e.g. see 
http://jeb.biologists.org/content/208/9/1717.long ) That might well be 
an univeral rule of thumb, an attractor state that comes about because 
of the tradeoffs between metabolism, time to build a body of a certain 
size, and reproduction. If so, then it might hold true for most alien 
life too.

Of course, that scaling suggests that *very* large creatures could fit 
your demand. A thousand ton creature living for a thousand years doesn't 
sound too far-fetched, assuming it makes ecological sense and lives in a 
liquid environment (there is an upper limit to land animals because of 
the square-cube law).

(To get to a million year lifespan the scaling requires about 10^16 kg 
mass, about the same as the entire Earth biosphere. That sounds unlikely.)

-- 
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University